Refrigerating system and control therefor



Get. 31, 1939. J, w. [CANNON 2,178,200

REFfiIGERATING SYSTEM AND .CONTROL THEREFOR Filed NOV. 5, 1937 l A? /320 i I INVENTOfl.

M, M M

ATTORNEY.

Patented Oct. 31, 1939 UNITED STATES-PATENT OFFICE arias sermons-nussits-rim m con'rno John W. cannon. Pennington, N. 1. ApplicationNovember 5,- 1931, Serial No. 11:;950 claims. (01. ss-o This inventionrelates generally to a refrig erating apparatus and more particularly toa single control therefor which will regulate during normalperformanceand will prevent exi cessive accumulation of ice or frostupon the evaporator;

In refrigerating systems of evaporator-expansion typ units have beenprovided having defrosting thermostats for automatically defrosting theevaporators. One of such defrosting thermostats is disclosed in my priorPatent No. 2,049,413 issued August 4, 1936, wherein the defrostingthermostat is operable to render the normal control means ineflectivewhen a predetermined amount of ice or frost has accumulated on theevaporator.

The main object of this invention is to provide a refrigerating systemwith a single thermostat which will function to control the temlperature 'of the cooling compartment in. the usual manner until a partthereof has become coated with a layer of ice spreading thcreoverfrom-the evaporator, and will thereupon automatically function todiscontinue the operation of the evaporator until the layer of icehas'melt-.

ed, whereupon it will again function as the normal control. r

I accomplish this result by arranging the thermostat adjacent to thebottom of the evaporator and in sucha position that a certain portionthereof is disposed in heat conducting relation to the evaporator and acertain portion thereof is disposed in the path of thethermo-siphoniiflly circulating air. In the preferred embodiment 35 ofmy invention, I make use of a thermostat which preferably consists of acylindrical bulb about three inches long -and having an outside diameterof about of an inch.. The bulb of the thermostat is preferablypositioned so that (0 it has a line about one-half inch. The remainingportion of the bulb. or about 2 inches thereof, is disposed so that itwill be wiped eifectively by the thermosiphonically circulating airlathe cooling cham-' her. The thermostat is preferably set to cut in ormake the'circuit at about 33 F. 'and to cut out or break the circuit atabout 28' I. when the thermostat ispontioned as described. the thermallycirculatins air passing over the ex- 60 posed portion thereof permits itto act as a normal control and to regul tion of the thermostat which isadjacent to the I evaporator, it serves to conduct the lower tenthe,compressorcontact with the evaporator forthe temperature of the coolingchamber. when a layer of. ice spreads from the evaporator onto thatpot-- perature in the evaporator to the thermostat. Then the temperatureof thethermostat as a whole is reduced rapidly by the low temperature ofthe portion which is in contact with the evaporator, whereupon thethermostat operates to i break the circuit and to stop the compressor;

which remains inactive until the layer of ice has substantially melted,whereupon the thermostat will again function as a normal control.

Further and more limited objects of the mvention will appear as thedescription proceeds in connection-with the accompanying drawing, inwhich Hg. 1 is a somewhat diagrammatic view of a refrigerating systemembodying my invention; Fig. 2 is a fragmentarysection'al view on theline 2-! of Fig. 1; Fig. 3-is a fragmentary view illustrating a modifiedform of my invention, and Fig. 4 is a fragmentary sectional view on theline 4-4 of Fig. 3.

In the drawing,.I have disclosed a refrigerating system which includes acoo ing chamber i in Y which is an evaporator 2 (or a brine tank ifdesired) which has flat surfaces thereon indicated by the referencecharacter 3. The reference character 4 designates a compressor which isoperated by an electric motor 5 through themedium or a belt 3. Disposedin contact with the surface 3 is a thermostat I which serves both as anormal control thermostat and as a defrosting thermostat. Thisthermostat consists 80 of a tube about three inches minimum length andhaving an outside diameter of about inch.

As shown in Figs. 1 and 2. the inner end of the tube has a line contactwith the surface I of the evaporator or brine tank for-a distance ofabout ,5 inch. The outer end of the tube projects outwardly for adistance of approximately 2% inches, and is so positioned as to be wipedeffectively by circulating air in the of the gas in-the bulb to thecut-out point, is governedby' the temperature of the evaporator orbrinetank and the temperature of a the air circulating over the exposedportion of the bulb. The thermostat of course actuates the switch t tomake and break the circuit to the motor which operates the compressor.Leading from one side ofthe line is a wire 9 which connects with aterminal I I of the switch I, and leading from the oppositeiterminal H-of the .switch is a wire I! which connects with one terminal I! of theelectric motor I which operates the compressor. leadins from teris minalI 4 of the motor is a wire II which connects with the opposite side ofthe line.

The compressor and the motor are supported upon the base member, whichis constructed to provide a receiver tank 16. Leading from the receivertank It is a pipe I 8 which communicates with the evaporator 2. Arrangedwithin the float chamber of the evaporator is a float I! which operatesa valve and serves to maintain a constant level of refrigerant in theevaporator. The liquid refrigerant, preferably S02, is admitted from thefloat chamber into the chilling unit of the evaporator where itevaporates, absorbing heat from the interior of the cooling chamberLeading from the evaporator is a pipe II which communicates with thecompressor, 4, and leading from the compressor is a pipe 22 whichcommunicates with the receiver 23, from which a return pipe 24communicates with the receiver tank It.

Theo'uter end of the thermostat may be supported by a bracket 25 securedto the wall of the cooling chamber.

In Fig. 3 there' is disclosed a slightly modified form of my inventionin which the thermostat 1 is supported by a bracket 25" secured to thewall of the cooling chamber and insulated from the evaporator by a block26 of approximately the shape and size shown, spacing the thermostatapproximately inch from the evaporator, and which is preferably formedof porcelain or glass or other suitable material having substantiallythe same heat conductivity as ice. In other respects, this form of theinvention is similar to and operates generally in the same manner asthat disclosed in Figs. 1 and 2.

My invention is also applicable to refrigerating systems of the gasfired or generator-condenser type, wherein the thermostat will operate avalve for controlling the rate of evaporation of refrigerant.

It will now be clear that I have provided a control for refrigeratingsystems which will accomplish the objects of the invention ashereinbefore stated. It is of course to be understood that theembodiments of the invention herein disclosed are to be consideredmerely as illustrative and not in a limiting sense as various changesmay be made in details of arrangement without departing from the spiritof my invention.

Having thus described my invention, what I claim is:

1. The combination with a refrigerator cabinet including a coolingchamber, of a refrigerant circuit including an evaporator for coolingsaid chamber, and a single thermostat for controlling the rate ofevaporation of refrigerant and for defrosting the evaporator, and meanssupporting said thermostat in such fixed relation with respect to thelower portion of said evaporator that a portion at one end of thethermostat may be aflfected by the building up of ice on said portion ofthe evaporator and initiate a defrosting cycle, while the rest of thethermostat projects freely away from the evaporator into the path of aircirculating through the cooling chamber, said projecting portion beingof such extent as, to cause the thermostat to respond to temperaturechanges insaid chamber and to exert normal control of the refrigerantcircuit.

2. An arrangement of the type set forth in claim 1 wherein the portionof the thermostat which may be aiiected by the building up of ice onthelower portion of the evaporator is in line contact with saidevaporator.

3. An arrangement of the type set forth in claim 1 wherein the portionof the thermostat which may be aflfe'cted by the building up of ice onthe lower portion of the evaporator is spaced from the said portion by amaterial having substantially the same heat conductivity as ice.

JOHN W. CANNON.

